1. Field of the Invention
The present invention relates to an image pickup apparatus, method and computer-readable recording medium and, more particularly, to an image pickup apparatus, image pickup method, and computer-readable recording medium which can implement suitable appropriate exposure control even when objects having extremely different luminance contrasts exist at the same field angle.
2. Related Background Art
Conventionally, xe2x80x9ccenter-weighted photometryxe2x80x9d is extensively used as a photometry system for exposure control. In this xe2x80x9ccenter-weighted photometryxe2x80x9d, as shown in FIG. 1, the average luminance signal level of an entire frame (inside a whole screen frame 201) is calculated by integration. Similarly, the average luminance signal level of a central portion (inside a center frame 202) is calculated by integration. These signal levels are combined to generate an exposure evaluation signal attaching importance to an object (inside the center frame 202) in the center of the screen, thereby performing photometry.
This xe2x80x9ccenter-weighted photometryxe2x80x9d conventionally widely used, however, is based on the assumption that a main object is present in the center of the screen. Therefore, if a main object exists in a position deviated from the screen central portion (e.g., inside the center frame 202), photometry (exposure control) is performed for an object other than this main object.
For example, if, as shown in FIG. 2, the dress of a person in black is present in the center of the screen and his or her face is in the upper central portion, exposure is so controlled that the black clothes in the center are appropriately exposed. Consequently, control is so performed as to open the iris, and the face of the person as a main object is overexposed. Note that FIGS. 1 and 2 are views for explaining the exposure control operation of a conventional image pickup apparatus.
Also, if objects having extremely different luminance contrasts exist in the same screen, exposure is controlled such that an object in the center of the screen is fixedly accentuated. Accordingly, a target object is excessively underexposed or overexposed.
As described above, the conventional image pickup apparatus controls exposure for an object present in the center of the screen. Therefore, if objects having exceptionally different luminance contrasts exist in the same screen, a target object is extremely underexposed or overexposed.
It is an object of the present invention to provide an image pickup apparatus, image pickup method, and computer-readable recording medium capable of suitable appropriate exposure control even when objects having excessively different luminance contrasts exist at the same field angle.
To achieve the above object, according to an aspect of the present invention, there is provided an image pickup apparatus comprising an image pickup region including a plurality of divided photometry frames, first calculating means for calculating an average value a1 of a predetermined number of divided photometry frames in the image pickup region, second calculating means for calculating an average value a23 of a smaller number of divided photometry frames than the predetermined number in the image pickup region, and exposure control means for controlling exposure by using signals from the first and second calculating means.
According to another aspect, there is provided an image pickup apparatus comprising an image pickup region including a plurality of divided photometry frames, an integral circuit for calculating an average value a1 of a predetermined number of divided photometry frames in the image pickup region, and an average value a23 of a smaller number of divided photometry frames than the predetermined number in the image pickup region, and a control circuit for controlling exposure on the basis of an output signal from the integral circuit.
According to still another aspect, there is provided a method of controlling an image pickup apparatus including an image pickup region having a plurality of divided photometry frames, comprising the first calculation step of calculating an average value a1 of a predetermined number of divided photometry frames in the image pickup region, the second calculation step of calculating an average value a23 of a smaller number of divided photometry frames than the predetermined number in the image pickup region, and the exposure control step of controlling exposure by using the average values a1 and a23.
According to still another aspect, there is provided a storage medium storing a control program for controlling an image pickup apparatus including an image pickup region having a plurality of divided photometry frames, the control program comprising a first code of controlling the apparatus to calculate an average value a1 of a predetermined number of divided photometry frames in the image pickup region, a second code of controlling the apparatus to calculate an average value a23 of a smaller number of divided photometry frames than the predetermined number in the image pickup region, and a third code of controlling the apparatus to control exposure by using the average values a1 and a23.
According to still another aspect, there is provided a storage medium storing a control program for controlling an image pickup apparatus including an image pickup region having a plurality of divided photometry frames, the control program comprising a first code of calculating an average value a1 of a predetermined number of divided photometry frames in the image pickup region, a second code of calculating an average value a23 of a smaller number of divided photometry frames than the predetermined number in the image pickup region, and a third code of controlling exposure by using the average values a1 and a23.
Other objects, features and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings.